ZHCSCX2E January 2014 – October 2017 LM15851
PRODUCTION DATA.
Within the DDC, eight different frequency and phase settings are always available for use. Each of the eight settings uses a different phase accumulator within the NCO. Because all eight phase accumulators are continuously running independently, rapid switching between different NCO frequencies is possible allowing rapid tuning of different signals.
The specific frequency-phase pair in use is selected through either the NCO_x input pins, or the NCO_SEL configuration bits (register 0x20D, bits 2:0). The CFG_MODE bit (register 0x20C, bit 0) is used to choose whether the input pins or selection bits are used. When the CFG_MODE bit is set to 0, the NCO_x input pins select the active NCO frequency and phase setting. When the CFG_MODE bit is set to 1, the NCO_SEL register settings select the active NCO frequency and phase setting.
The frequency for each phase accumulator is programmed independently through the NCO_FREQn (and optionally NCO_RDIV) settings. The phase offset for each accumulator is programmed independently through the NCO_PHASEn register settings.